EUV optics

ABSTRACT

In a first aspect, a method of fabricating an EUV light source mirror is disclosed which may comprise the acts/steps of providing a plurality of discrete substrates; coating each substrate with a respective multilayer coating; securing the coated substrates in an arrangement wherein each coated substrate is oriented to a common focal point; and thereafter polishing at least one of the multilayer coatings. In another aspect, an optic for use with EUV light is disclosed which may comprise a substrate; a smoothing layer selected from the group of materials consisting of Si, C, Si 3 N 4 , B 4 C, SiC and Cr, the smoothing layer material being deposited using highly energetic deposition conditions and a multilayer dielectric coating. In another aspect, a corrosion resistant, multilayer coating for an EUV mirror may comprise alternating layers of Si and a compound material having nitrogen and a 5 th  period transition metal.

The present application is related to co-pending U.S. patent applicationSer. No. 11/174,299 filed on Jun. 29, 2005 and entitled, LPP EUV LIGHTSOURCE DRIVE LASER SYSTEM, attorney docket number 2005-0044-01, U.S.Pat. No. 6,625,191 granted on Sep. 23, 2003 and entitled, VERY NARROWBAND, TWO CHAMBER, HIGH REP RATE GAS DISCHARGE LASER SYSTEM and U.S.Pat. No. 6,549,551 granted on Apr. 15, 2003 and entitled, INJECTIONSEEDED LASER WITH PRECISE TIMING CONTROL and U.S. Pat. No. 6,567,450granted on Apr. 20, 2003 and entitled, VERY NARROW BAND, TWO CHAMBER,HIGH REP RATE GAS DISCHARGE LASER SYSTEM, the entire contents of whichare hereby incorporated by reference herein.

FIELD

The present disclosure relates to extreme ultraviolet (EUV) lightgenerators providing EUV light from a plasma created from a sourcematerial and collected and directed to a focus for utilization outsideof the EUV light source generation chamber, e.g., for semiconductorintegrated circuit manufacturing photolithography e.g., at wavelengthsof around 50 nm and below.

BACKGROUND

EUV light, e.g., electromagnetic radiation having wavelengths of around50 nm or less (also sometimes referred to as soft x-rays) and includinglight at a wavelength of about 13.5 nm, can be used in photolithographyprocesses to produce extremely small features in substrates, e.g.,silicon wafers.

Methods to produce EUV light include, but are not necessarily limitedto, converting a material into a plasma state that has an element, e.g.,xenon, lithium or tin, indium, antimony, tellurium, aluminum, etc. withan emission line in the EUV range. In one such method, often termedlaser-produced plasma (LPP) the required plasma can be produced byirradiating a target material, such as a droplet, stream or cluster ofmaterial having the required line-emitting element, with a laser beam.

Once generated, the EUV light is typically reflected by a multi-layermirror, sometimes called a collector mirror. For example, in one setup,a normal incidence elliptical reflector may be used having an apertureto allow laser light to pass through and reach the target material at anirradiation site. In one arrangement, a collector in the shape of aprolate ellipsoid may be positioned such that its first focus is locatedat the irradiation site and its second focus is positioned at aso-called intermediate point (also called the intermediate focus) wherethe EUV light may be output from the light source and input to, e.g., anintegrated circuit lithography tool.

Some lithography tools utilize an arc field illumination field toefficiently irradiate the tool's photomask/reticle. For example, seeU.S. Pat. No. 6,210,865 entitled “EXTREME-UV LITHOGRAPHY CONDENSOR”which issued to Sweatt et al on Apr. 3, 2001, the contents of which ishereby incorporated by reference herein. Thus, for this type of tool,the EUV light generated at the plasma irradiation site may need to becollected, condensed and shaped to create the arc field. Typically, forEUV light, reflective optics, e.g., grazing and/or normal incidencemirrors, are used, with each reflection resulting in an in-bandintensity loss of about 20-40%. Thus, it may be desirable to use as fewoptics as possible between the plasma irradiation site and thephotomask/reticle.

Another factor that is often considered when designing a high volume EUVlight source is the generation and mitigation of debris which may damageEUV light source optics such as a laser input window, collector mirrorand/or metrology equipment. Thus, for at least some source materials,the production of a plasma may also generate undesirable by-products inthe plasma chamber, (e.g., debris) which can potentially damage orreduce the operational efficiency of the various plasma chamber opticalelements. This debris can include out-of-band photons, high energy ionsand scattered debris from the plasma formation, e.g., atoms and/orclumps/microdroplets of source material. This debris may also includechamber material from secondary sputtering and for the case of electricdischarge type systems, electrode material. For this reason, it is oftendesirable to employ one or more techniques to minimize the types,relative amounts and total amount of debris formed for a given EUVoutput power. When the target size, e.g., droplet diameter, and/ortarget makeup, e.g., chemistry, are chosen to minimize debris, thetargets are sometimes referred to as so-called “mass limited” targets.

The high energy ions and/or source material debris may be damaging tothe optical elements in a number of ways, including heating them,coating them with materials which reduce light transmission, penetratinginto them and, e.g., damaging structural integrity and/or opticalproperties, e.g., the ability of a mirror to reflect light at such shortwavelengths, corroding or eroding them and/or diffusing into them. Thus,debris reduction and/or suitable techniques to reduce the impact ofdebris may need to be considered in the design of a high volume EUVlight source.

One way to reduce the influence of debris is to move the collectormirror away from the irradiation site. This, in turn, implies the use ofa larger collector mirror to collect the same amount of light. Theperformance of a collector mirror, e.g., the ability to accuratelydirect as much in-band light as possible to, e.g., a focal point,depends of the figure and surface finish, e.g., roughness of thecollector. As one might expect, it becomes more and more difficult toproduce a suitable figure and surface finish as the size of thecollector mirror grows. Typically, these EUV collector mirrors haveincluded a monolithic substrate overlaid with a multilayer dielectriccoating, e.g., Mo/Si. Depending on the application, these multilayermirrors may also include thin barrier layers deposited at one or moreinterfaces and in some cases can include a capping layer. Collectormirror substrate requirements may include one or more of the following:vacuum compatibility, mechanical strength, e.g. high temperaturestrength, high thermal conductivity, low thermal expansion, dimensionalstability, ability to be polished to a suitable figure and finish, andthe ability to be brazed or bonded.

With the above in mind, Applicants disclose EUV optics includingcollector mirrors, corresponding fabrication methods, and methods ofuse.

SUMMARY

In a first aspect, a method of fabricating an EUV light source mirror isdisclosed which may comprise the acts/steps of providing a plurality ofdiscrete substrates; securing the substrates in an arrangement whereineach substrate is oriented to a common focal point; and thereafterpolishing at least one of the substrates and coating each the substratewith a respective EUV reflective multilayer coating. The mirror may be anormal incidence mirror or a grazing incidence mirror. In oneimplementation the arrangement comprises an ellipsoid, and in oneparticular implementation, the ellipsoid has a diameter greater than 500mm. In one embodiment the plurality of substrates may comprises ninesubstrates. The act/step of securing the coating substrates may beaccomplished by bonding and/or brazing.

In another aspect, an optic for use with EUV light is disclosed whichmay comprise a substrate; a smoothing layer selected from the group ofmaterials consisting of Si, C, Si₃N₄, B₄C, SiC and Cr, the smoothinglayer material being deposited using highly energetic depositionconditions; and a multilayer coating overlying the smoothing layer. Thehighly energetic deposition conditions may include substrate heatingand/or increasing particle energy during deposition. In one embodimentthe smoothing layer overlays and contacts the substrate and in oneparticular embodiment the substrate comprises SiC. By way of example,the smoothing layer may have a thickness in the range of 3 nm to 100 nmand may comprise an amorphous material. In one implementation,multilayer coating comprises alternating layers of Mo and Si and in oneparticular implementation, the optic is a collector mirror for an EUVlight source.

In a particular aspect, a method for producing an optic for use with EUVlight may comprise the steps/acts of providing a substrate; depositing asmoothing layer on the substrate; polishing the smoothing layer; andoverlying a multilayer EUV coating the smoothing layer. In some cases,the method may further comprise the step of polishing the substrate. Forexample, the substrate may comprise SiC and the smoothing layer maycomprise crystalline Si deposited to a thickness in the range of about 5μm to 100 μm.

In one aspect of an embodiment, a method of fabricating a normalincidence, EUV light source mirror may comprise the steps/acts ofproviding a plurality of discrete substrates, at least one of thesubstrates fabricated by replication from a master pattern; coating eachthe substrate with a respective normal incidence EUV reflectivemultilayer coating; and securing the coated substrates together to forma single mirror. The substrate may comprise nickel, e.g., a nickelalloy. In one implementation, one or more (or in some cases all) of thesubstrates may be deformable, e.g., nickel alloy having a thickness inthe range of about 0.5 mm to about 1.5 mm. In another implementation,one or more (or in some cases all) of the substrates may be rigid, e.g.,nickel alloy having a thickness in the range of 3.5 mm to 6.5 mm. Aplurality of the substrates may be fabricated by replication from acommon master pattern, and in some cases, the substrates may befabricated by an electroforming replication process.

For one aspect, an EUV light source mirror assembly may comprise asupport structure and a plurality of discrete substrates with eachsubstrate coated with a respective EUV reflective multilayer coating andat least one of the substrates may be moveably mounted on the supportstructure to allow adjustment of the substrate relative to the supportstructure. For example, the mirror assembly may include an actuator,e.g., an actuator having an electro-actuatable element, e.g.,piezoelectric, for moveably mounting the substrate to the supportstructure. In one arrangement, the substrate may be deformable andactivation of the actuator may deform the substrate. In anotherarrangement, the substrate may be rigid and activation of the actuatormay translate the substrate relative to the support structure. Thesubstrate may be mounted on a common support structure and the supportstructure may be made of a low coefficient of thermal expansion materialsuch as si-carbon fiber composite, SiC, invar or stainless steel. In oneembodiment, the mirror assembly may include a plurality of rings with atleast one substrate mounted on at least one ring; and an actuator formoveably mounting at least one ring relative to the support structure.In a particular embodiment, at least one substrate is mounted on aplurality of rings and the substrate may be deformable.

Another aspect includes a method for fabricating and aligning a lightsource collector mirror that may comprise the steps/acts of providing asupport structure; coating a plurality of discrete substrates with anEUV reflective multilayer coating; using an actuator to moveably mountat least one of the substrates to the support structure and activatingthe actuator to adjust at least one of the substrates relative to thesupport structure. In one implementation, the mirror may be anellipsoidal mirror establishing first and second focal points and themethod may further comprise the steps of directing light, e.g., lighthaving a frequency in the visible spectrum, from the first focal pointtoward the mirror for measurement at the second focal point and usingthe measurement to activate the actuator and align the substrate. Theactivating step may be performed after installation of the mirror in alight source, e.g., in a plasma chamber of an LPP light source, andwhile the mirror is at elevated temperature.

In another aspect of an embodiment, normal incidence, EUV light sourcecollector mirror for receiving light directly from an EUV light emittingplasma and producing a shaped beam for use with a system illuminating alithography mask with an illumination field having a pre-selected shape,e.g., arc shaped, in a plane normal to the direction of lightpropagation is provided. The collector mirror may comprise a supportstructure and a plurality of facets, each facet having an outline shape,and wherein the pre-selected shape of the illumination field and theoutline shape of the facet are substantially the same. For this aspect,each facet may comprise a rotationally symmetric reflective surface andthe facets may be mounted on the support structure and aligned to directbundles of light toward a plurality of focal spots. For example, therotationally symmetric reflective surface may be an off-axis surfacesegment of a sphere, a surface segment of an asphere or an on-axissurface segment of a toroid. In one implementation, at least one facetis arc shaped and in a particular implementation, the mirror maycomprise over 50 facets. Several arrangements are contemplated includingan arrangement in which the facets are positioned in a generallyellipsoidal pattern, an arrangement in which the facets are positionedin a generally parabolic pattern and an arrangement in which the facetsare positioned in a generally near-parabolic pattern. In one setup, aplurality of actuators are provided, with each actuator moveablymounting a respective facet to the support structure.

In still another aspect of an embodiment, an optical arrangement forhomogenizing and shaping light from an EUV light emitting plasma to amask as an illumination field having a pre-selected shape, e.g., arcshaped, in a plane normal to the direction of light propagation isdisclosed. The arrangement may comprise an EUV reflective mirrorcomprising a plurality of reflective surfaces and a normal incidence,EUV light source collector mirror for receiving light directly from theplasma, the collector mirror having a plurality of facets with eachfacet having an outline shape, and wherein the pre-selected shape of theillumination field and the outline shape of the facet are substantiallythe same. For this aspect, the arrangement may further comprise an EUVlight condenser mirror. In one embodiment, the reflective surfaces ofthe EUV reflective mirror may be arranged in a generally planar patternand in a particular embodiment, the facets of the collector mirror maycomprise a rotationally symmetric reflective surface.

In another aspect, a corrosion resistant, multilayer coating for an EUVmirror may comprise a plurality of bi-layers with each bi-layer having alayer comprising Si and a layer comprising a compound material havingnitrogen and a 5^(th) period transition metal (e.g., Y, Zr, Nb, Mo, Ru,Rh, Pd, Ag or Cd). In one embodiment, the 5^(th) period transition metalis selected from the group of metals consisting of Nb, Mo and Ru and ina particular embodiment, the compound material is a nitride, e.g., MoN,MoNbN or NbN.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of an overall broad conception for alaser-produced plasma EUV light source;

FIG. 2 shows a flow chart illustrating process steps/acts forfabricating an EUV light source mirror;

FIG. 3 shows a front view of an elliptical EUV collector mirror that hasbeen fabricated by bonding/brazing nine coated substrates together;

FIG. 4 is an enlarged sectional view of an EUV optic illustrating asmoothing layer;

FIG. 5 is an enlarged, not to scale, sectional view of a multilayersystem;

FIG. 5A is an enlarged, not to scale, sectional view of an alternativeembodiment of an MLM mirror having a relatively thick smoothing layer;

FIG. 6 shows a front view of an elliptical, normal incidence, EUVcollector mirror that has been fabricated by securing eight identicallyshaped coated substrates together;

FIG. 7 shows an example of a monolithic, honeycomb support structure fora collector mirror;

FIG. 8 shows an example of a monolithic, equilaterial triangular rib,support structure for a collector mirror;

FIG. 9 illustrates a collector mirror wherein multiple coated substratesmay be moveably mounted on a support structure to allow adjustment ofeach substrate relative to a support structure using actuators;

FIG. 10 shows a schematic of an optical arrangement for homogenizing andshaping light from an EUV light emitting plasma to a mask as anarc-shaped illumination field;

FIG. 11 shows a front view of a multi-faceted collector mirror for usein the arrangement shown in FIG. 10;

FIG. 12 shows a perspective view a mirror facet for use in the collectormirror shown in FIG. 11;

FIG. 13 shows a front view of a multi-faceted pupil mirror for use inthe arrangement shown in FIG. 10;

FIG. 14 shows an example of a dimensioned, arc shaped illumination fieldsuitable for irradiating an EUV photomask/reticle;

FIG. 15 is an enlarged, not to scale, sectional view of a corrosionresistant multilayer mirror; and

FIG. 16 shows calculated reflectivities for multilayer mirrors havingMoN/Si bi-layers, NbN/Si bilayers and MoNbN/silicon bi-layers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With initial reference to FIG. 1 there is shown a schematic view of anexemplary EUV light source, e.g., a laser produced plasma EUV lightsource 20 according to one aspect of an embodiment. As shown, the LPPlight source 20 may include a pulsed or continuous laser source 22,e.g., a pulsed gas discharge CO₂ laser source producing radiation at10.6 μm, e.g. with DC or RF excitation operating at relatively highpower and high pulse repetition rate. For example, a suitable CO₂ lasersource having a MO-PA1-PA2-PA3 configuration is disclosed in co-pendingU.S. patent application Ser. No. 11/174,299 filed on Jun. 29, 2005, andentitled, LPP EUV LIGHT SOURCE DRIVE LASER SYSTEM, attorney docketnumber 2005-0044-01, the entire contents of which were previouslyincorporated by reference herein.

Depending on the application, other types of lasers may also besuitable. For example, a solid state laser, an excimer, a molecularfluorine laser, a MOPA configured excimer laser system, e.g., as shownin U.S. Pat. Nos. 6,625,191, 6,549,551, and 6,567,450, an excimer laserhaving a single chamber, an excimer laser having more than two chambers,e.g., an oscillator chamber and two amplifying chambers (with theamplifying chambers in parallel or in series), a master oscillator/poweroscillator (MOPO) arrangement, a power oscillator/power amplifier (POPA)arrangement, or a solid state laser that seeds one or more CO₂, excimeror molecular fluorine amplifier or oscillator chambers, may be suitable.Other designs are possible.

As further shown in FIG. 1, the light source 20 may also include asource material delivery system 24, e.g., delivering droplets of asource material into the interior of a chamber 26 to a target volume 28where the source material targets will be irradiated by one or morelight pulses, e.g., a pre-pulse and thereafter a main pulse, to producea plasma and generate an EUV emission. The source material may include,but is not limited to, a material that includes tin, lithium, xenon orcombinations thereof. The EUV emitting element, e.g., tin, lithium,xenon, etc., may be in the form of liquid droplets and/or solidparticles contained within liquid droplets or any other form thatdelivers the EUV emitting element to the target volume.

Continuing with FIG. 1, the light source 20 may also include a collector30, e.g., a normal incidence reflector, e.g., in the form of a truncatedellipse, e.g., a multi-layer mirror having alternating layers ofMolybdenum and Silicon, with an aperture to allow the light pulsesgenerated by the source 22 to pass through and reach the target volume28. The collector 30 may be, e.g., an elliptical mirror that has a firstfocus within or near the target volume 28 and a second focus at aso-called intermediate point 40 (also called the intermediate focus 40)where the EUV light may be output from the light source 20 and input to,e.g. an integrated circuit lithography tool (not shown).

The light source 20 may also include an EUV light source controllersystem 60, which may also include a firing control system 65 fortriggering one or more lamps and/or laser sources in the source 22 tothereby generate light pulses for delivery into the chamber 26. Inaddition, the light source 20 may include a droplet position detectionsystem which may include one or more droplet imagers 70 that provide anoutput indicative of the position of one or more droplets, e.g.,relative to the target volume 28 and provide this output to a dropletposition detection feedback system 62, which can, e.g., compute adroplet position and trajectory, from which a droplet error can becomputed, e.g., on a droplet by droplet basis or on average. The dropleterror may then be provided as an input to the light source controller60, which can, e.g., provide a position, direction and timing correctionsignal to the source 22 to control a source timing circuit and/or tocontrol a beam position and shaping system e.g., to change the locationand/or focal power of the light pulses being delivered to the chamber26.

As shown in FIG. 1, the light source 20 may include a droplet deliverycontrol system 90, operable in response to a signal (which in someimplementations may include the droplet error described above, or somequantity derived therefrom) from the system controller 60, to e.g.,modify the release point of the source material from a droplet deliverymechanism 92 to correct for errors in the droplets arriving at thedesired target volume 28.

FIG. 2 shows a flow chart illustrating process steps/acts forfabricating a relatively large EUV light source mirror such as theellipsoidal mirror 30 shown in FIGS. 1 and 3. It is to be appreciatedthat the fabrication process shown is not necessarily limited to normalincidence mirrors, collector mirrors or mirrors having any particularshape, e.g., ellipsoidal, but instead may be used to produce other largeEUV optics such as grazing incidence mirrors, including mirrors designedto reflect at incident angles greater than twenty degrees, sphericalmirrors, aspherics, etc.

As shown in FIG. 2, a method of fabricating an EUV light source mirrormay begin by preparing a plurality of discrete substrates (box 100).Next, as shown in FIG. 2, the substrates are then positioned in anarrangement which approximates the final, desired figure of the opticalelement (box 102). For example, for an ellipsoid collector mirror, eachcoated substrate may be positioned and tested to establish the firstellipsoid focus (e.g., point 28 in FIG. 1), the second ellipsoid focus(e.g. point 40 in FIG. 1), or both. Once a suitable arrangement isobtained, the substrates are secured together (box 104). The act/step ofsecuring may be accomplished by bonding and/or brazing. Other fasteningtechniques, e.g., mechanical fasteners, may be used in lieu of bondingand/or brazing, or in addition thereto to secure the coated substratestogether. After assembly, the substrates may be polished (as anassembly) to obtain the final figure and surface finish for the optic(box 106). Once polished, each substrate in the assembly may be coatedwith a multilayer coating such as a Mo/Si dielectric coating (box 108).

Cross referencing FIGS. 1 and 3, it can be seen that nine substrates110, 112 a-h, including a central ellipsoidal shaped substrate 110 andeight peripheral substrates 112 a-h, may be arranged as a single,relatively large ellipsoid mirror 30, allowing, in some cases, anellipsoid having a diameter, d, greater than 500 mm. Although anembodiment with nine substrates 110, 112 a-h is shown, it is to beappreciated that more than nine and as few as two substrates may bejoined together using the procedure described herein. For someapplications, use of the above-described techniques may allow the use ofsingle crystal silicon to create mirrors sizes that would be otherwisetechnically and/or economically unfeasible, however, nothing in thisdisclosure should be interpreted to limit the fabrication method to anyspecific type of substrate material or size.

FIGS. 4 and 5 illustrate a coating for an optical element substrate,such as a collector mirror 30 shown in FIG. 1. As described herein, thecoatings and coating processes illustrated in FIGS. 4 and 5 may be usedon multi-substrate mirrors such as the mirror 30 shown in FIGS. 1 and 3,single substrate, e.g., monolithic mirrors, normal incidence mirrorssuch as collector mirrors, grazing incidence mirrors (e.g. low angle(<20 degrees) grazing incidence mirrors which typically use metalliccoatings, e.g., Ruthenium, and high angle (20-40 degrees) grazingincidence mirrors which typically use multilayer coatings, e.g.,dielectric multilayer coatings, e.g., Mo/Si multilayer coatings. Inaddition, the coatings and coating processes illustrated in FIGS. 4 and5 may be used on any other EUV optics that are coated with a multi-layercoating.

Beginning with FIG. 4, for use with 13 nm light, the substrate 118 a maybe made of silicon including single crystal and polycrystallinematerial, glidcop, float glass, ULE glass (ultra-low expansion glass),Zerodur, fused silica, aluminum, beryllium, molybdenum, copper, nickelor nickel alloy, silicon carbide including high density SiC and otherdensities, SiC produced by various techniques such as CVD SiC, CVC SiC,reaction-bonded SiC, and other composites containing SiC or othersuitable substrate materials that are known or become known in thepertinent art. The coating may include a layer 130 which may be aso-called smoothing layer that is deposited on the substrate 118 a tooverlay and contact a surface of the substrate, as shown. FIG. 4 showsthat the coating may further include a multilayer system 132 overlayingthe layer 130. As used herein, the term “smoothing layer” and itsderivatives, includes, but is not necessarily limited to a layer whichpromotes a smooth finish in subsequently applied layers which overlaythe smoothing layer and may perform this function by creating a smoothsurface for the subsequent layer(s), including the topcoat, that areoverlaid on the smoothing layer, the smooth surface of the smoothinglayer being created either as-deposited or after subsequent operations,e.g., polishing, etc.

In particular, the use of smoothing layer(s) may be suitable on opticswhich may be difficult to polish, e.g., aspherical optics, however, theymay also have application for other optics, e.g., flat optics andspherical optics. The smoothing layer may also be applied to smoothenand improve the surface conditions of a used EUV optic (that may havesuffered erosion, debris deposition, contamination, etc.) before it isre-coated with a multilayer coating.

In one embodiment, the layer 130 may include a smoothing layer materialsuch as Si, C, Si₃N₄, B₄C, SiC, Cr, CrSi₂, MoC₂ or MoSi₂ that has beendeposited using highly energetic deposition conditions. The highlyenergetic deposition conditions may include substrate heating and/ordepositing the material using increased particle energy, as compared tostandard deposition techniques. As used herein, the term “particle” andits derivatives includes, but is not limited to ions and neutrals of aparticular chemical element or molecule. For example, the substrate maybe heated to a temperature in the range of about 100 to 200 degrees C.

The high energy supplied during deposition (either by substrate heatingor by increasing the energies of ions and neutrals during deposition)may increase the atomic mobility on the surface during deposition whichin turn may lead to a smoothening. Typical ion energies may be in therange of several 100 eV to a few 1000 eV. A grazing ion incidence anglemay be used to obtain a smooth surface through ion polishing. In somecases, it may be advantageous to first treat the surface by ionbombardment for some length of time before the smoothing layer isdeposited. This may lead to the elimination of the roughest features onthe substrate surface before the application of the smoothing layer.

Although FIG. 4 shows a single smoothing layer 130, the disclosureprovided herein is not limited to a single smoothing layer depositedduring a single continuous deposition process. Instead, multiplesmoothing layers may be applied, differing in smoothing material and/ortime of deposition and other processing steps may be performed, e.g.,polishing, etc. between depositions. For example, smoothing layers canbe applied followed by ion bombardment polishing and subsequentapplication of another smoothing layer. Each layer may be applied with adifferent duration. Also, different energies of ion bombardment withargon ions or other sputter ions may be used during or betweendeposition periods.

The layer 30 may be deposited using deposition techniques known in thepertinent art such as, but not limited to, physical vapor deposition bythermal source or electron beam, or ion assisted deposition. Prior todeposition of the layer 130, the substrate may be cleaned using one ormore of the following techniques to include ultrasonic aqueous cleaningand/or solvent cleaning, for example using high purity Methanol or someother suitable solvent. In some cases, and for some materials, e.g.carbon and Silicon Nitride, the layer 130 may be deposited to athickness “t” below a critical thickness in which crystallization occursto obtain a substantially amorphous coating. 12. For some embodiments,the smoothing layer may have a thickness in the range of 3 nm to 100 nm.The thickness used will typically dependent on the materials used (e.g.substrate and smoothing material). For example, for Si, a thickness of5-20 nm may be used, and for chromium, a thickness of 20-40 nm may beused.

In some cases, a high degree of substrate smoothing may provided throughamorphous layer growth initiated through multivalent chemical bonds withsurface atoms during sufficiently energetic deposition conditions. Thus,in addition to carbon (C) and silicon (Si), thin layers of carbon orsilicon containing compounds like SiC, B₄C, Si₃N₄ may be suitable.Chromium or CrSi₂ may also form a good smoothing layer due to its growthproperties, e.g., 20 nm-40 nm thick amorphous layers of chromium can begrown for a wide range of deposition parameters.

FIG. 5 illustrates in greater detail a multilayer system 132 that may bedeposited on layer 130 shown in FIG. 4. As shown there, the multilayersystem 132 may include plurality of bi-layers 134 a, 134 b, 134 c, whichmay or may not be graded across the face of the mirror. For themultilayer system 132, each bi-layer may include a layer of a firstdielectric material having an index of refraction, n₁, and a layer of asecond dielectric material having an index of refraction, n₂, withn₁≠n_(2.) For example, for the system 132 shown, the bi-layer 134 a mayhave a layer 136 a of Molybdenum (Mo) and a layer 136 b of silicon (Si),the bi-layer 134 b may have a layer 138 a of Mo and a layer 138 b of Si,and the bi-layer 134 c may have a layer 140 a of Mo and a layer 140 b ofSi. In some designs, each layer of the multilayer system 132 may have alayer thickness which may be approximately λ/4, (and in some cases λ/2)where λ is a selected center wavelength for light illuminating theoptic, e.g., 13 nm. Each layer of the multilayer system 132 may bedeposited using one of the techniques described above.

FIG. 5A illustrates an alternative embodiment of an MLM mirror 142having a smooth surface finish. For this embodiment, a substrate 144,which may be, for example, SiC is first prepared, and in some casespolished. Then, a relatively thick smoothing layer 146, e.g.,crystalline Si at a thickness in the range of about 5 μm to 100 μm, andin some cases about 10 μm to 25 μm, is deposited. The smoothing layercan be deposited using e-beam evaporation, and typically, the energeticconditions described above may not be necessary. The smoothing layer canthen be polished, e.g., using atomic polishing, and then coated with amulti-layer coating 148, as shown.

FIG. 6 shows a front view of an elliptical, normal incidence, EUVcollector mirror that has been fabricated by securing together eightidentically shaped coated substrates 150 a-h, e.g., substrates coatedwith EUV normal incidence, multilayer coatings. For the mirror shown inFIG. 6, each substrate 150 a-h may be fabricated by replication from amaster pattern. For example, this replication may be performed using anelectroforming replication process, wherein a material, e.g., a nickelalloy is deposited, e.g., by galvanic deposition, onto the masterpattern and thereafter separated, e.g., using thermal separationtechniques, e.g., taking advantage of the coefficient of thermalexpansion difference between the nickel alloy and the pattern material.Using this process, substrates of nickel alloy having a thickness in therange of about 0.5 mm to about 1.5 mm may be obtained to producedeformable substrates and substrates of nickel alloy having a thicknessin the range of 3.5 mm to 6.5 mm may be obtained to produce a relativelyrigid substrate. Replication from a common master pattern may result ina relatively inexpensive production technique for producing relativelylarge EUV mirrors. Although eight substrates 150 a-h are used for themirror shown in FIG. 6, it is to be appreciated that the replicationtechnique disclosed here can be used to produce mirrors having more thaneight and as few as one substrates, (e.g., to produce multiple mirrors)and that the technique may be used to produce mirrors having someidentical substrates and some non-identical substrates (such as themirror shown in FIG. 3).

Multiple substrates, such as the substrates 150 a-h shown in FIG. 6 maybe secured together by bonding, brazing and/or mechanical fastening,e.g., bolting. For example, the substrates 150 a-h may be secured to acommon, e.g., monolithic, support structure such as the honeycombsupport structure 700 shown in FIG. 7 or the equilateral triangular ribstructure 800 shown in FIG. 8. For the nickel alloy replicatedsubstrates, it may be desirable to fabricate the support structure of anickel alloy to facilitate brazing and so that the substrates andsupport structure have similar or identical coefficients of thermalexpansion. Other suitable materials for the support structure mayinclude low coefficient of thermal expansion materials such as Si-carbonfiber composite, SiC, invar or stainless steel.

FIG. 9 illustrates an embodiment of a collector mirror 30″ whereinmultiple substrates 900 a-h may be moveably mounted on a supportstructure to allow adjustment of each substrate 900 a-h relative to thesupport structure via actuators 902 a-p. For the embodiment shown, thesupport structure can include a plurality of rings 904, 906 with thecorners of each substrate 900 a-h attached to an actuator 902 a-p, whichin turn is attached to one of the rings 904, 906. In anotherarrangement, the substrates may be rigidly attached to the rings, whichare then moveable attached, via one or more respective actuators to asupport structure such as one of the structures shown in FIGS. 7 or 8.In yet another arrangement, the substrates may be moveable attached, viaone or more respective actuators to a support structure, (i.e., withoutrings) such as one of the structures shown in FIGS. 7 or 8.

For the collector mirror 30″, the actuators 902 a-p may have anelectro-actuatable element, e.g., piezoelectric, for moveably mountingthe substrate to the support structure. As used herein, the term“electroactuatable element” and its derivatives, means a material orstructure which undergoes a dimensional change when subjected to avoltage, electric field, magnetic field, or combinations thereof andincludes but is not limited to piezoelectric materials, electrostrictivematerials and magnetostrictive materials.

As indicated above, each substrate 900 a-h may be deformable andactivation of one of the actuators 902 a-p may deform the substrate. Inanother arrangement, each substrate 900 a-h may be rigid and activationof one or more of the actuators 902 a-p may translate a substrate 900a-h relative to the support structure. In some cases, the adjustment ofthe substrates 900 a-h via actuators 902 a-p may be performed afterinstallation of the mirror 30″ in a light source, e.g. in a plasmachamber of an LPP light source, and while the mirror 30″ is at elevatedtemperature and/or under high vacuum. For this case, the actuators maybe made using a high temperature, piezoelectric material, e.g., apiezoelectric rated for 150 degree C. service.

A procedure for fabricating and aligning a light source collector mirrormay be described with cross-reference to FIGS. 1 and 9. As shown in FIG.1, the ellipsoidal mirror establishes a first focal point 28 and asecond focal point 40, which may be used to align the collector mirror30 and/or one or more of the individual substrates making up thecollector mirror. Thus, the procedure may be employed for a mirrorhaving a one-piece, e.g., monolithic substrate, multiple substratessecured together to form a rigid construction, or multiple substratesthat are adjustably moveable relative to a support structure/ringsand/or to each other.

For the procedure, a source of light may be positioned inside the plasmachamber and oriented to direct light, e.g., light having a frequency inthe visible spectrum, from the first focal point, e.g., point 28 towardthe mirror 30 for measurement at the second focal point, e.g., point 40.This measurement may then be used to selectively activate one or more ofthe actuators 902 a-p and align the one or more of the substrates 900a-h. The measurement and activation steps may be performed afterinstallation of the mirror 30 in a light source, e.g., in a plasmachamber of an LPP light source, and while the mirror 30 is at elevatedtemperature and/or under high vacuum.

FIG. 10 illustrates an optical arrangement (designated generally 1000)for collecting and/or homogenizing and/or shaping light from an EUVlight emitting plasma 1002 to a plane 1004, e.g., mask plane, as ashaped, e.g., arc shaped or rectangular shaped, illumination field,i.e., a beam having pre-selected shape, e.g., arc or rectangular, in aplane normal to the general propagation direction (see also FIG. 14). Asshown, the arrangement 1000 may include an EUV light source collectormirror 1006, an EUV reflective mirror 1008, e.g. a pupil mirror, and acondenser mirror 1010. Generally, as shown, a portion of the light fromthe plasma 1002 first reaches the collector mirror 1006 where it isreflected and directed to the mirror 1008 where it is reflected anddirected to the condenser mirror 1010 where it is reflected and directedto the plane 1004.

Cross-referencing FIGS. 10 and 11, it can be seen that the collectormirror 1006 may include plurality of individual facets, of which facets1012 a-c have been labeled with reference numerals. Although severalhundred facets are shown in FIG. 11, it is to be appreciated that morethan several hundred and as few as two facets may be used in thecollector mirror 1006. More particularly, it is contemplated that about50 to 1000 facets may be used.

FIG. 12 shows an example of a facet 1012 for use in the collector mirror1006. For the collector mirror 1006, one or more of the facets 1012 mayhave a reflective surface 1014 having an outline shape (which for thefacet shown in FIG. 12 is arc-shaped) that is substantially the sameshape as the selected shape of the illumination field, i.e., the shapein a plane normal to the direction of light propagation at thelithography mask. Thus, for an arc-field lithography tool, the facets1012 may have an outline shape that is arc shaped, for a rectangularfield lithography tool, the facets 1012 may have an outline shape thatis rectangular shaped, etc.

Use of a mirror pair downstream of an EUV light source having amulti-faceted mirror with arc shaped facets to produce an arc field hasbeen previously disclosed in an article titled “FABRICATION OF ACOMPLEX-SHAPED MIRROR FOR AN EXTREME ULTRAVIOLET LITHOGRAPH ILLUMINATIONSYSTEM” written by Takino et al. and published in Opt. Eng. 42(9) inSeptember 2003 and in “NOVEL ILLUMINATION SYSTEM FOR EUVL” written byKomatsuda and published in Proc. SPIE 3997, 765-776 (2000), both ofwhich are hereby incorporated by reference herein.

For the arrangement 1000, each facet 1012 may have a concaverotationally symmetric reflective surface 1014, e.g., an off-axissurface segment of a sphere, a surface segment of an asphere or anon-axis surface segment of a toroid. Further, each facet 1012 may becoated with a normal incidence EUV reflective coating, e.g., multi-layerdielectric coating, e.g., Mo/Si coating. More than one, and in someimplementations all, of the collector mirror facets may be identical.Also, more than one, and in some cases all, of the collector mirrorfacets may be manufactured using a replication process as describedabove, or can be cut, lapped and polished pieces. By way of example, andnot limitation, each facet 1012 may be rectangular and arc shaped asshown in FIG. 12 and may have a length “L” of about 40 mm, a width “W”of about 10 mm and a thickness “T” of about 1 mm. With this shape, afill factor of about 90% may be achieved.

FIG. 10 illustrates that the facets 1012 a-c may be mounted on a supportstructure 1016 and arranged in a pattern, e.g., periodic pattern whichmay be, for example, generally ellipsoidal, generally parabolic orgenerally near-parabolic pattern. Within the general pattern, each facet1012 a-c may be aligned, individually to direct a bundle of light towarda particular spot, thus, the alignment may be non-uniform from facet1012 to facet 1012.

In one setup, actuators 1018 may be provided, e.g., an actuator havingan electro-actuatable element, e.g., piezoelectric, with one or moreactuators moveably mounting a respective facet to the support structuree.g. two actuators may be provided to provide two axis, e.g. tip-tiltcontrol. Alternatively, an arrangement may be provided (not shown) inwhich one actuator may move one or more facets. The actuators may beutilized to align the facets 1012 prior to operation of the lightsource/lithography tool and/or during operation and may be operated inresponse to a control signal, e.g., generated by an optical detector,e.g., photodetector array, wavefront sensor, etc.

A better understanding of the mirror 1008, e.g. pupil mirror, can beobtained with cross-reference to FIGS. 10 and 13. As shown the mirror1008 may include plurality of individual facets, of which facets 1020a-c have been labeled with reference numerals. Although only a portion,e.g., about twenty facets, are shown in FIG. 13, it is to be appreciatedthat the entire operable surface of the mirror 1008 may be covered withfacets 1020.

FIG. 13 shows that the facets 1020 may be hexagonal shaped and placed inan arrangement which fills space to reduce intensity loss. Each facet1020 may be coated with a normal incidence EUV reflective coating, e.g.,multi-layer dielectric coating, e.g., Mo/Si coating. More than one, andin some implementations all, of the facets 120 may be identical. Also,more than one, and in some cases all, of the mirror facets 1020 may bemanufactured using a replication process as described above, or can becut, lapped and polished pieces. By way of example, and not limitation,each facet 1020 may be hexagonal shaped as shown in FIG. 12 and may havea width of about 10-30 mm.

FIG. 10 illustrates that the facets 1020 a-c may be mounted on a supportstructure 1024 and arranged in a pattern, e.g., periodic pattern whichmay be, for example, planar, as shown. Within the general pattern, eachfacet 1020 a-c may be aligned, individually to direct a bundle of lighttoward a particular spot on the condenser mirror 1010, thus, thealignment may be non-uniform from facet 1020 to facet 1020.

In one setup, actuators 1026 may be provided, e.g. an actuator having anelectro-actuatable element, e.g., piezoelectric, with one or moreactuators moveably mounting a respective facet to the support structure,e.g. two actuators may be provided to provide two axis, e.g., tip-tiltcontrol. Alternatively, an arrangement may be provided (not shown) inwhich one actuator may move one or more facets 1020. The actuators maybe utilized to align the facets 1020 prior to operation of the lightsource/lithography tool and/or during operation and may be operated inresponse to a control signal, e.g., generated by an optical detector,e.g., photodetector array, wavefront sensor, etc.

From the multi-faceted mirror 1008, light may be condensed by condensermirror 1010 onto plane 1004 as shown in FIG. 10. For example mirror 1010may be a concave, EUV normal incidence mirror, e.g., having amulti-layer dielectric coating, e.g., Mo/Si coating. FIG. 14 illustratesa dimensioned, arc shaped illumination field 1028 at the plane 1004,e.g., photomask/reticle plane.

FIG. 15 illustrates in greater detail a multilayer system 1132 that maybe deposited on a substrate 118 a and/or layer 130 (see FIG. 4). Asshown in FIG. 15, the multilayer system 1132 may include plurality ofbi-layers 1134 a, 1134 b, 1134 c, which may or may not be graded acrossthe face of the mirror. For the multilayer system 1132, each bi-layermay include a layer of a first dielectric material having an index ofrefraction, n₁, and a layer of a second dielectric material having anindex of refraction, n₂, with n₁≠n_(2.) For example, for the system 1132shown, the bi-layer 1134 a may have a layer 1136 a including a compoundmaterial having nitrogen and one or more 5^(th) period transition metals(e.g., Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag and Cd) and a layer 1136 b ofsilicon (Si). In particular, nitrogen compounds of Y, Zr, Nb, Mo, Ru,Rh, Pd (and their alloys) show relatively good reflectivity for lightwith a wavelength between 13 nm and 14 nm.

These corrosion resistant, EUV-reflective, multilayer coatings may beused in environments which tend to oxidize inferior materials. Ingeneral, oxide layers may lead to relatively large absorption of EUVlight, e.g., light around 13.5 nm wavelength and may cause to coating todegrade. Thus, in most cases, if oxidation can be avoided, a higherreflectance of the mirror can be sustained and a longer mirror lifetimemay be expected. One source of oxidation may arise due to the relativelyhigh water vapor content that is typically present in the plasma vacuumchamber and/or the coating may be exposed to oxygen contact when thechamber is vented. When debris mitigation etchants, e.g., HBr gas, areemployed, the silicon layers may be etched away more rapidly than theother bi-layer material (e.g., Mo, for a standard Mo/Si MLM) allowingmolybdenum oxide layers to form on the top of the multilayer coating.Also, it is possible that over time, several layers may be etched awayby ion bombardment from the plasma and/or by etching, e.g., from an HBrcleaning gas.

In general, transition metal nitrides, e.g., TM_(x)N_(y) are moreresistant to oxidation than their pure transition metal. In addition,layer intermixing tends to be relatively low for the nitride. Therefore,MLM coatings having transition metal nitrides may also have improvedhigh-temperature stability. Although some transition metal nitrides,e.g., MoN, absorbs more strongly at 13.5 nm than their pure transitionmetal e.g., Mo, the reflectivity may still be suitable. By using aplurality of bi-layers, and in some cases, all bi-layers havingtransition metal nitrides, sacrificial layers may be etched by plasmaion bombardment or halogen-containing cleaning gas while maintaining ancorrosion resistant surface.

In some designs, each layer of the multilayer system 1132 may have alayer thickness which may be approximately λ/4, (and in some cases λ/2)where λ is a selected center wavelength for light illuminating theoptic, e.g., 13.5 nm. Each layer of the multilayer system 132 may bedeposited using one of the techniques described above. In someimplementations, the nitridation may be introduced during deposition bythe admixture of nitrogen to the sputter gas (i.e., by reactivesputtering). For this implementation, the degree of nitridation may bevaried and the total nitrogen content of the layers can be reduced belowa 1:1 stochiometric nitrogen content. This may increase the reflectivitydue to the reduction of nitrogen absorbers. It may also be possible touse an MoRu alloy target instead of pure Mo or pure Ru. In this caseMoRuN is formed (Mo_(x)Ru_(y)N_(z)). Of the relevant transition metals,ruthenium is particularly resistant to oxidation. Therefore, a lowerdegree of nitridation may be applied when Ru or Ru-containing alloys areused for the transition metal layer.

FIG. 16 shows calculated reflectivities for multilayer mirrors havingMoN/Si bi-layers, NbN/Si bilayers and MoNbN/silicon bi-layers. RuN andRhN layers (not shown) give slightly lower peak reflectivities. For thecalculation, a layer ratio of 0.4 was used and the number of layers usedwas 60. Interface roughness is not taken into account. The layer periodfor MoN was 6.90 nm, for NbN it was 6.88 nm and for MoNbN it was 6.89nm. For MoNb, a 1:1 alloy mixture was assumed. As shown, the calculatedpeak reflectivity is in the range of about 67 to 69%, however, theachievable reflectivity values will typically be lower, e.g., around 55%due to the finite layer roughness.

It will be understood by those skilled in the art that aspects ofembodiments of the subject matter disclosed above are intended tosatisfy the requirement of disclosing at least one enabling embodimentof the subject matter of each claim and to be one or more such exemplaryembodiments only and to not to limit the scope of any of the claims inany way and particularly not to a specific disclosed embodiment alone.Many changes and modification can be made to the disclosed aspects ofembodiments of the disclosed subject matter of the claims that will beunderstood and appreciated by those skilled in the art, particularly inregard to interpretation of the claims for purposes of the doctrine ofequivalents. The appended claims are intended in scope and meaning tocover not only the disclosed aspects of embodiments of the claimedsubject matter but also such equivalents and other modifications andchanges that would be apparent to those skilled in the art. In additionsto changes and modifications to the disclosed and claimed aspects of thesubject matter disclosed of the present invention(s) noted above, otherscould be implemented.

While the particular aspects of embodiment(s) of the EUV OPTICSdescribed and illustrated in this patent application in the detailrequired to satisfy 35 U.S.C. §112 is fully capable of attaining anyabove-described purposes for, problems to be solved by or any otherreasons for or objects of the aspects of an embodiment(s) abovedescribed, it is to be understood by those skilled in the art that it isthe presently described aspects of the described embodiment(s) of thesubject matter claimed are merely exemplary, illustrative andrepresentative of the subject matter which is broadly contemplated bythe claimed subject matter. The scope of the presently described andclaimed aspects of embodiments fully encompasses other embodiments whichmay now be or may become obvious to those skilled in the art based onthe teachings of the Specification. The scope of the present EUV OPTICSis solely and completely limited by only the appended claims and nothingbeyond the recitations of the appended claims. Reference to an elementin such claims in the singular is not intended to mean nor shall it meanin interpreting such claim element “one and only one” unless explicitlyso stated, but rather “one or more”. All structural and functionalequivalents to any of the elements of the above-described aspects of anembodiment(s) that are known or later come to be known to those ofordinary skill in the art are expressly incorporated herein by referenceand are intended to be encompassed by the present claims. Any term usedin the Specification and/or in the claims and expressly given a meaningin the Specification and/or claims in the present application shall havethat meaning, regardless of any dictionary or other commonly usedmeaning for such a term. It is not intended or necessary for a device ormethod discussed in the Specification as any aspect of an embodiment toaddress each and every problem sought to be solved by the aspects ofembodiments disclosed in this application, for it to be encompassed bythe present claims. No element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element in the appended claims is to be construedunder the provisions of 35 U.S.C. § 112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited as a “step” instead of an“act.”

It will be understood also be those skilled in the art that, infulfillment of the patent statutes of the United States, applicant(s)has disclosed at least one enabling and working embodiment of eachinvention recited in any respective claim appended to the Specificationin the present application and perhaps in some cases only one. Forpurposes of cutting down on patent application length and drafting timeand making the present patent application more readable to theinventor(s) and others, applicant(s) has used from time to time orthroughout the present application definitive verbs (e.g., “is”,“are”,“does”, “has”, “includes” or the like) and/or other definitive verbs(e.g., “produces,” “causes” “samples,” “reads,” “signals” or the like)and/or gerunds (e.g., “producing,” “using,” “taking,” “keeping,”“making,” “determining,” “measuring,” “calculating” or the like), indefining an aspect/feature/element of, an action of or functionality of,and/or describing any other definition of an aspect/feature/element ofan embodiment of the subject matter being disclosed. Wherever any suchdefinitive word or phrase or the like is used to describe anaspect/feature/element of any of the one or more embodiments disclosedherein, i.e., any feature, element, system, sub-system, component,sub-component, process or algorithm step, particular material, or thelike, it should be read, for purposes of interpreting the scope of thesubject matter of what applicant(s) has invented, and claimed, to bepreceded by one or more, or all, of the following limiting phrases, “byway of example,” “for example,” “as an example,” “illustratively only,”“by way of illustration only,” etc., and/or to include any one or more,or all, of the phrases “may be,” “can be”, “might be,” “could be” andthe like. All such features, elements, steps, materials and the likeshould be considered to be described only as a possible aspect of theone or more disclosed embodiments and not as the sole possibleimplementation of any one or more aspects/features/elements of anyembodiments and/or the sole possible embodiment of the subject matter ofwhat is claimed, even if, in fulfillment of the requirements of thepatent statutes, applicant(s) has disclosed only a single enablingexample of any such aspect/feature/element of an embodiment or of anyembodiment of the subject matter of what is claimed. Unless expresslyand specifically so stated in the present application or the prosecutionof this application, that applicant(s) believes that a particularaspect/feature/element of any disclosed embodiment or any particulardisclosed embodiment of the subject matter of what is claimed, amountsto the one an only way to implement the subject matter of what isclaimed or any aspect/feature/element recited in any such claim,applicant(s) does not intend that any description of any disclosedaspect/feature/element of any disclosed embodiment of the subject matterof what is claimed in the present patent application or the entireembodiment shall be interpreted to be such one and only way to implementthe subject matter of what is claimed or any aspect/feature/elementthereof, and to thus limit any claim which is broad enough to cover anysuch disclosed implementation along with other possible implementationsof the subject matter of what is claimed, to such disclosedaspect/feature/element of such disclosed embodiment or such disclosedembodiment. Applicant(s) specifically, expressly and unequivocallyintends that any claim that has depending from it a dependent claim withany further detail of any aspect/feature/element, step, or the like ofthe subject matter of what is claimed recited in the parent claim orclaims from which it directly or indirectly depends, shall beinterpreted to mean that the recitation in the parent claim(s) was broadenough to cover the further detail in the dependent claim along withother implementations and that the further detail was not the only wayto implement the aspect/feature/element claimed in any such parentclaim(s), and thus be limited to the further detail of any suchaspect/feature/element recited in any such dependent claim to in any waylimit the scope of the broader aspect/feature/element of any such parentclaim, including by incorporating the further detail of the dependentclaim into the parent claim.

1. A method of fabricating an EUV light source mirror, said methodcomprising the acts of: providing a plurality of discrete substrates;securing said substrates in an arrangement wherein each substrate isoriented to a common focal point; and thereafter polishing at least oneof said substrates; coating each said substrate with a respective EUVreflective multilayer coating.
 2. A method as recited in claim 1 whereinsaid mirror is a normal incidence mirror.
 3. A method as recited inclaim 1 wherein said arrangement establishes an ellipsoidal mirror.
 4. Amethod as recited in claim 3 wherein said ellipsoidal mirror has adiameter greater than 500 mm.
 5. An optic for use with EUV light, saidoptic comprising; a substrate; a smoothing layer selected from the groupof materials consisting of Si, C, Si₃N₄, B₄C, SiC and Cr, said smoothinglayer material being deposited using highly energetic depositionconditions; and a multilayer EUV coating overlying said smoothing layer.6. An optic as recited in claim 5 wherein said deposition conditionsinclude substrate heating.
 7. An optic as recited in claim 5 whereinsaid deposition conditions include increasing particle energy duringdeposition.
 8. An optic as recited in claim 5 wherein said substratecomprises SiC.
 9. An optic as recited in claim 5 wherein said smoothinglayer overlays and contacts said substrate.
 10. An optic as recited inclaim 5 wherein said multilayer coating comprises alternating layers ofMo and Si.
 11. An optic as recited in claim 5 wherein said optic is acollector mirror for an EUV light source.
 12. An optic as recited inclaim 5 wherein said smoothing layer has a thickness in the range of 3nm to 100 nm.
 13. An optic as recited in claim 5 wherein said smoothinglayer comprises an amorphous material.
 14. A method for producing anoptic for use with EUV light, said method comprising the steps of:providing a substrate; depositing a smoothing layer on the substrate;polishing the smoothing layer; and overlying a multilayer EUV coatingsaid smoothing layer.
 15. A method as recited in claim 14 wherein saidsmoothing layer is selected from the group of materials consisting ofSi, C, Si₃N₄, B₄C, SiC and Cr.
 16. A method as recited in claim 14wherein said smoothing layer is deposited to a thickness in the range of5 μm to 100 μm.
 17. A method as recited in claim 14 further comprisingthe step of polishing the substrate.
 18. A method as recited in claim 14wherein said substrate comprises SiC and said smoothing layer comprisesSi deposited to a thickness in the range of 5 μm to 100 μm.
 19. A methodas recited in claim 14 wherein said smoothing layer comprises acrystalline material.
 20. A method of fabricating a normal incidence,EUV light source mirror, said method comprising the acts of: providing aplurality of discrete substrates, at least one of said substratesfabricated by replication from a master pattern; coating each saidsubstrate with a respective normal incidence EUV reflective multilayercoating; and securing said coated substrates together to form a singlemirror.
 21. A method as recited in claim 20 wherein each said substratecomprises Nickel.
 22. A method as recited in claim 20 wherein each saidsubstrate is deformable.
 23. A method as recited in claim 22 whereineach said substrate has a thickness in the range of 0.5 mm to 1.5 mm.24. A method as recited in claim 20 wherein each said substrate isrigid.
 25. A method as recited in claim 24 wherein each said substratehas a thickness in the range of 3.5 mm to 6.5 mm.
 26. A method asrecited in claim 20 wherein a plurality of the substrates are fabricatedby replication from a common master pattern.
 27. A method as recited inclaim 20 wherein said substrates are fabricated by an electroformingreplication process.
 28. An EUV light source mirror assembly comprising:a support structure; and a plurality of discrete substrates, eachsubstrate coated with a respective EUV reflective multilayer coating; atleast one of said substrates moveably mounted on said support structureto allow adjustment of said substrate relative to said supportstructure.
 29. A mirror assembly as recited in claim 28 furthercomprising an actuator for moveably mounting said substrate to saidsupport structure.
 30. A mirror assembly as recited in claim 29 whereinsaid actuator comprises an electro-actuatable element.
 31. A mirrorassembly as recited in claim 29 wherein said substrate is deformable andactivation of said actuator deforms said substrate.
 32. A mirrorassembly as recited in claim 29 wherein said substrate is rigid andactivation of said actuator translates said substrate relative to saidsupport structure.
 33. A mirror assembly as recited in claim 28 whereineach said substrate is mounted on a common support structure.
 34. Amirror assembly as recited in claim 28 wherein said support structure ismade of a material selected from the group of low coefficient of thermalexpansion materials consisting of si-carbon fiber composite, SiC, invarand stainless steel.
 35. A mirror assembly as recited in claim 28further comprising: a plurality of rings with at least one substratemounted on at least one ring; and an actuator for moveably mounting atleast one ring relative to said support structure.
 36. A mirror assemblyas recited in claim 35 wherein at least one substrate is mounted on aplurality of rings.
 37. A mirror assembly as recited in claim 36 whereinsaid substrate is deformable.
 38. A method for fabricating and aligninga light source collector mirror, said method comprising the steps of:providing a support structure; coating a plurality of discretesubstrates with an EUV reflective multilayer coating; using an actuatorto moveably mount at least one of said substrates to said supportstructure, and activating said actuator to adjust at least one of thesubstrates relative to the support structure.
 39. A method as recited inclaim 38 wherein said mirror is an ellipsoidal mirror establishing firstand second focal points and said method further comprises the steps of:directing light from the first focal point toward the mirror formeasurement at the second focal point, the light having a frequency inthe visible spectrum; and using the measurement to activate the actuatorand align the substrate.
 40. A method as recited in claim 38 whereinsaid activating step is performed after installation of the mirror in alight source and while the mirror is at elevated temperature.
 41. Anormal incidence, EUV light source collector mirror for receiving lightdirectly from an EUV light emitting plasma and producing a shaped beamfor use with a system illuminating a lithography mask with anillumination field having a pre-selected shape in a plane normal to thedirection of light propagation, said mirror comprising: a supportstructure; a plurality of facets, each facet having an outline shape,and wherein the pre-selected shape of the illumination field and theoutline shape of the facet are substantially the same.
 42. A collectormirror as recited in claim 41 wherein the facets are shaped as arcs. 43.A collector mirror as recited in claim 41 wherein said mirror comprisesover 50 facets.
 44. A collector mirror as recited in claim 41 whereinthe facets are positioned in a generally ellipsoidal pattern.
 45. Acollector mirror as recited in claim 41 wherein the facets arepositioned in a generally parabolic pattern.
 46. A collector mirror asrecited in claim 41 wherein the facets are positioned in a generallynear-parabolic pattern.
 47. A collector mirror as recited in claim 41further comprising a plurality of actuators, each actuator moveablymounting a respective facet to the support structure.
 48. A collectormirror as recited in claim 41 wherein at least one facet comprises anoff-axis surface segment of a sphere.
 49. A collector mirror as recitedin claim 41 wherein at least one facet comprises a surface segment of anasphere.
 50. A collector mirror as recited in claim 41 wherein at leastone facet comprises an on-axis surface segment of a toroid.
 51. Anoptical arrangement for homogenizing and shaping light from an EUV lightemitting plasma to a mask as an illumination field having a pre-selectedshape in a plane normal to the direction of light propagation, thearrangement comprising: an EUV reflective mirror comprising a pluralityof reflective surfaces; a normal incidence, EUV light source collectormirror for receiving light directly from the plasma, the collectormirror having a plurality of facets with each facet having an outlineshape, and wherein the pre-selected shape of the illumination field andthe outline shape of the facet are substantially the same.
 52. Anarrangement as recited in claim 51 further comprising an EUV lightcondenser mirror.
 53. An arrangement as recited in claim 51 wherein saidreflective surfaces of said EUV reflective mirror are arranged in agenerally planar pattern.
 54. An arrangement as recited in claim 51wherein said facets of said collector mirror comprise a rotationallysymmetric reflective surface.
 55. An arrangement as recited in claim 51wherein the facet outline is arc shaped.
 56. A corrosion resistant,multilayer coating for an EUV mirror, the coating comprises a pluralityof bi-layers, each bi-layer comprising: a layer comprising Si; and alayer comprising a compound material having nitrogen and a 5^(th) periodtransition metal.
 57. A coating as recited in claim 56 wherein the5^(th) period transition metal is selected from the group of metalsconsisting of Y, Zr, Nb, Mo, Ru, Rh and Pd.
 58. A coating as recited inclaim 56 wherein the 5^(th) period transition metal is selected from thegroup of metals consisting of Nb, Mo and Ru.
 59. A coating as recited inclaim 56 wherein the compound material is a nitride.
 60. A coating asrecited in claim 56 wherein the compound material is a MoN.
 61. Acoating as recited in claim 56 wherein the compound material is a MoNbN.62. A coating as recited in claim 56 wherein the compound material is aNbN.